Such an energy cell is known from US 2011/0024075, for example, in which an energy cell is described in the form of a cylinder and a movable piston in the cylinder that encloses a chamber in the cylinder that is filled with such a phase-change material, which expands upon the transition from a solid to a liquid state due to heating, and thereby moves the piston in the cylinder, whereby this movement can be used to exert a mechanical force.
Due to the alternating heating and cooling of the phase-change material in the cylinder, the phase-change material can be made to melt and solidify alternately and thus expand and contract in volume, which results in an in-and-out movement of the piston, whereby this movement can be converted into a motion for driving a motor or other device.
Another example of an energy cell is known from the international patent application WO 2010/074616 in which an energy cell is described in the form of a cylindrical pressure vessel with an elastic bladder therein that is filled with a hydraulic fluid, and which extends axially through the pressure vessel in a space surrounded by a casing of phase-change material with which the space between the pressure vessel and the bladder is filled. Upon a volume increase of the phase-change material, hydraulic fluid is squeezed out of the aforementioned bladder and the volume displacement of the hydraulic fluid arising therefrom is used to generate hydraulic energy.
Such an energy cell is more efficient than the construction in the form of a piston-cylinder as there are no friction losses when an elastic bladder squeezes together.
A disadvantage of an energy cell as described in WO 2010/074616 is that the diameter of the bladder undergoes relatively large changes as a result of volume changes, which results in relatively high stresses in the material of the bladder and in time results in a short lifetime of the bladder.
Another disadvantage is that when the bladder squeezes together, folds can occur that can weaken the bladder locally or even close off parts of the bladder, such that the hydraulic fluid in these parts is prevented from escaping, such that particularly high pressures can be built up in these parts that do not contribute to the conversion into useful hydraulic energy, and which constitute a risk of the bladder tearing.
Another disadvantage is that the construction of such an energy cell is relatively complex and that the assembly and replacement of the components is relatively complicated and takes up a lot of time.